1. Technical Field
A device for converting physiologically derived energy to electric energy while walking in a form of a low profile pneumatic electric power generator that is adapted for integration in a midsole of a shoe, to generate power as the wearer walks is disclosed. The midsole is also adapted to become a prime mover for the pneumatic electric generator, while doing its primary function of cushioning the foot. Thus, the present invention also relates to the design of a midsole of a shoe, specifically for the purpose of driving the pneumatic generator as well as cushioning the foot.
2. Prior Art
U.S. Pat. No. 3,857,7899 (1975) to Battle Development Corporation discloses a method and an apparatus for converting one form of energy into another form of energy. The method and apparatus uses a closed, continuous loop passageway containing a plurality of freely movable, mechanically unrestrained bodies which travel around the passageway in one direction only. Closed loop systems of this type, while are realizable, requires a mechanical flow control mechanism to ensure unidirectional motion. Unidirectional motion of the plurality of freely movable, mechanically unrestrained bodies does not seem to be key requirement for energy conversion.
The art of making of air hammers in well known. U.S. Pat. No. 3,894,586 (1975) to McDonnell Douglas Corporation disclosed a reciprocal air hammer in which the piston is driven in both directions. The unrestrained piston in the air hammer can be extended to a plurality of freely movable unrestrained bodies, moving back and forth in a closed passageway.
An air motor can be used to drive a conventional electric generator to generate electric power. Electric generators have been integrated in air tools, U.S. Pat. No. 5,525,842 (1996) to Volt-Aire Corporation, disclosed an improvement on an air motor having an integral generator, based on U.S. Pat. No. 4,678,922 (1987) to Leininger. In these patents the generation of electricity is to provide lighting to illuminate the work area while using the air tool. The electric generator is a part of the air tool rotor that is designed to develop the required torque for the operation of the tool. Magnets are inserted in the rotor and windings are set in the rotor housing to generate enough power for the light. This pneumatic electric generator is designed as a part of a tool driven by industrial type compressed air systems. While miniaturization of such a system is possible, it can not be easily integrated in applications with space constraints and operational conditions of a midsole of a shoe.
Integration of electric power generators into shoes has been proposed. For example, U.S. Pat. No. 4,782,602 (1988) and U.S. Pat. No. 4,845,338 (1989) both to Lakic, disclosed the design of a shoe with a foot warmer and an electric generator, driven by a coupling mechanism that translates the vertical movement of the heel to rotational motion. The power generated is only intended to warm the foot, and in a ski boot, the extra weight may not be a major problem. U.S. Pat., No. 5,167,682 (1992), and U.S. Pat. No. 5,495,682 (1996), to Chen disclosed the designs of "Dynamoelectric Shoes", with a pressure operated electric generator. The forces in the heel drive the generator through a set of levers and gears. These approaches do not utilize all the forces in the foot.
Martyn R. Shorten in Biomechanics Vol. 26, Supp. 1 pp 41-51, 1993, presented a detailed analysis of the energetics of running and running shoes and the midsole design objectives. The viscoelastic elements in the midsole are designed to dissipate the energy transferred into the midsole by the foot. In this approach the midsole is a shock absorber with a viscous dumper. The viscous damper is selected for its ability to dissipate the mechanical energy. In this invention the mechanical energy transferred into the midsole is harnessed and used instead of just dissipated. U.S. Pat. No. 5,224,278 (1993) to Jeon, is an example of a midsole with a shock absorbing airbags and viscoelastic elements to dissipate the energy.
In the development of the system to couple the mechanical energy in the foot during walking into the low profile pneumatic electric generator, it is necessary to use airbags with flow-check valves. The use of the flow-check valves with flappers is well established in inflatable products. There has not been a need to setup complex flow patterns in a midsole of a shoe, so the use of flow-check valves with airbags in midsoles has not been considered. Also the need to create pulsed-flows in a midsole of a shoe has not been realized.
The various approaches to integrating electric generators in shoes that have been attempted so far have not effectively collected most of the mechanical energy associated with the forces in the foot during walking. There are also excessive weight and reliability issues in some embodiments. Also there are problems associated with gyroscopic forces due to the spinning rotor. The goals for the design of shoe midsoles have been mainly to dissipate the mechanical energy. With the perforation of portable electronic devices, there is an obvious need to convert this energy into some usable form.